1. Field of the Invention
This invention relates to electrical switching apparatus such as power circuit breakers, network protectors and switches used in electric power circuits carrying large currents. Such apparatus utilizes a large spring to store sufficient energy to close the contacts of the apparatus against the sizeable magnetic repulsion forces generated by the large current while simultaneously charging opening springs. More particularly, the invention is directed to the operating mechanism which mounts, and controls the storage and release of energy, by the close spring. Specifically, it relates to the close prop which retains the close spring in the charged state ready for closing, the latch assembly which releases the close prop to initiate closing, and a reset device which resets the close prop and latch assembly.
2. Background Information
Electrical switching apparatus for opening and closing electric power circuits typically utilize an energy storage device in the form of one or more large springs to close the contacts of the device into the large currents which can be drawn in such circuits. Such electrical apparatus includes power circuit breakers and network protectors which provide protection, and electrical switches which are used to energize and deenergize parts of the circuit or to transfer between alternative power sources. These power circuit breakers, network protectors and switches also include an open spring or springs which rapidly separate the contacts to interrupt current flow in the power circuit. The open springs are charged during closing by the close spring which, therefore, must store sufficient energy to both overcome the mechanical and magnetic forces for closing, as well as to charge the open springs. As indicated, either or both of the close spring and open spring can be a single spring or multiple springs and should be considered as either even though the singular is hereafter used for convenience.
An operating mechanism mounts and controls the charging and discharge of the close spring. Typically, the operating mechanism includes a cam member which rotates in a single direction and is coupled to the close spring to charge the spring as the cam is rotated either manually, by a handle, or automatically, by a motor, through a ratchet mechanism. The ratchet mechanism introduces some backlash as the cam is incrementally rotated during the charge cycle. As the close spring becomes fully charged, the cam goes overcenter and the stored energy in the spring tends to drive the cam. A close prop holds the spring in the charged state. Typically, the close prop is spring biased to this latched state, and a release mechanism withdraws the close prop when the stored energy is to be released for closing the contacts of the electrical apparatus. As the close prop is typically biased to the latched state it is reset automatically after the spring is released and the cam is driven to a close position from which a new charge cycle can be initiated. This biasing of the close prop to the latched position increases the release force required. Hence, there is room for improvement in close props and the associated operating mechanism of power circuit breakers, network protectors and switches.
There is a need therefore for an improved operating mechanism for electrical switching apparatus such as power circuit breakers, network protectors and switches, and particularly the close prop which retains the close spring in the charged state.
In this regard, there is a need for an operating mechanism with a close prop having a lighter release force than is typically provided.
There is also a need for an improved operating mechanism in which the close prop is not biased to the latched position.
There is an additional need for such an operating mechanism having an arrangement for resetting the close prop to the latched position.